1. Field of the Invention
The present invention relates to hearing loss and, more particularly, to hearing loss evaluation and correction assistance.
2. Description of the Related Art
One out of ten people suffer from some degree of hearing loss. However, due to stigma, cost, and availability only about 25% of those who have hearing loss wear hearing aids. Many people do not want to wear hearing aids because they view hearing aids as a symbol of disability. In many countries (including the United States) hearing specialists, such as audiologists, perform hearing loss diagnosis. The diagnosis and subsequent fitting of a hearing aid device is a costly process. In developing countries, hearing specialists are rare and thus people of developing counties are often unable to get assistance. There are also many people with impaired hearing that are not aware that they have impaired hearing. Many people in this category are reluctant to spend the time and money to have their hearing examined by a hearing specialist.
More particularly, in most developed countries, hearing loss is diagnosed using specialized equipment known as an audiometer. Typically, a patient must visit a hearing specialists office or an ear, noise and throat (ENT) doctor's office to have hearing loss testing performed. If hearing loss is diagnosed, the hearing specialist or doctor will counsel the patient to consider using a hearing aid. If the patient chooses to purchase a hearing aid, the hearing specialist or doctor has to spend additional time to fit the hearing aid for the patient. All these services are expensive and usually not covered by insurance or the government.
As noted above, the conventional hearing loss testing is performed using an audiometer. The audiometer presents a calibrated pure tone signal to the patient via a transducer such as a headphone, an insert earphone, or a loud-speaker to one of the patients two ears. If the patient hears the tone, the level of the tone will be reduced and presented to the patient again. If the patient cannot hear the tone, the level of the tone will be increased and presented to a patient again. This procedure will repeat many times until certain number of reversals from decreasing the tone to increasing the tone has been reached. The hearing threshold of the patient is defined as the signal level at which the patient can hear the tone 50% percent of the time the tone is presented to the patient. The hearing threshold can be derived from the various reversal levels. For each ear, the above procedure is usually repeated at 125, 250, 500, 1000, 2000, 4000, and 8000 Hz. If the difference of the hearing thresholds at two adjacent frequencies exceeds a critical value (e.g., 20 dB), an additional test can be performed at a middle frequency. Often middle frequencies are only applied, when needed, for frequencies between 500 to 8000 Hz. Accordingly, the maximum number of testing frequencies is usually eleven (e.g., 125, 250, 500, 750, 1500, 2000, 3000, 4000, 6000, and 8000 Hz).
In order for the hearing loss test results to be meaningful, the testing system (namely, the audiometer) must be calibrated. In other words, the relationship between the electrical settings in the system and the acoustical pressure delivered to subject must be known. Various components affect the calibration including, but not limited to, electrical system that generates the stimuli and listening system (transducer) that converts electrical signal into acoustic pressure. Calibration is further complicated by the fact that sound level measured at the eardrum of a human varies from person to person even when delivered with the same system and identical settings. As a result, calibration of a testing system is often conventionally done using a special coupler for which a reference hearing level of normal listeners has been established. For example, the audiometer with an insertion earphone is usually calibrated in a 2 cubic-centimeters (cc) coupler. When listeners with normal hearing listen to pure tones through an insertion earphone, the sound levels, as measured in the 2 cc coupler, of the pure tones need to be set to the following levels (given in Sound Pressure Level (SPL)) for the sounds to be just audible:
Frequency (Hz) Level (dB SPL) 125 45 250 35 500 20 750 15 1000 10 1500 8 2000 7 3000 12 4000 20 6000 27 8000 30
The above levels are called normal reference levels of the insertion earphone in the 2 cc coupler. The reference levels vary for different transducers as well as different couplers.
Hearing thresholds for a patient are usually expressed in decibels hearing level (db HL), which is relative level in reference to the normal reference levels. The reference levels should have been established for the system and transducer used in the test. For example, the normal reference level for an insertion earphone is 7 dB SPL at 2000 Hz as measured in a 2 cc coupler. If the hearing level for a patient is 47 dB SPL at the same frequency as measured in the same 2 cc coupler, the hearing loss for the patient is 47-7=40 dB HL. For most commercial audiometers, the normal reference levels can be built-in the machine, and the signal level presented to patient is automatically expressed in dB HL.
Accordingly, there are various problems associated with conventional hearing loss testing. One problem with conventional hearing loss testing is that specialized testing equipment must be used and that the testing equipment must be calibrated. Another problem with conventional hearing loss testing is the costs and often limited availability of hearing specialists or ENT doctors to administrator the hearing loss examination. As a result, for various reasons, hearing loss testing and hearing loss assistance are generally not readily available to people.
Thus, there is a need for improved approaches to evaluating hearing loss and assisting those with hearing loss to obtain hearing assistance products or services.